The objective of this project is to understand control of lysogeny in Pl, a prophage that is not inserted into the host chromosome, as a model of a system for learning about the possible role of viruses (and/or episomes) in cancer. For the current year, we are investigating the growth of Pl in a dna ts E strain, a "DNA arrest" mutant of Pl, the interaction of Pl with a closely related temperate phage, and mutants affecting ability of Pl to lysogenize.